U.S. patent application number 16/295418 was filed with the patent office on 2019-09-12 for self-limiting regenerative pumping element start stage for high speed centrifugal engine fuel pump and associated method.
The applicant listed for this patent is EATON INTELLIGENT POWER LIMITED. Invention is credited to Martin A. Clements.
Application Number | 20190277233 16/295418 |
Document ID | / |
Family ID | 67843759 |
Filed Date | 2019-09-12 |
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United States Patent
Application |
20190277233 |
Kind Code |
A1 |
Clements; Martin A. |
September 12, 2019 |
SELF-LIMITING REGENERATIVE PUMPING ELEMENT START STAGE FOR HIGH
SPEED CENTRIFUGAL ENGINE FUEL PUMP AND ASSOCIATED METHOD
Abstract
An engine fuel or pump system includes a centrifugal pump having
an impeller for imparting energy to an associated fluid for an
associated downstream engine fuel system. A regenerative start
stage is in selective fluid communication with the pump. And
ejector includes an inlet that communicates with the pump outlet
and an outlet that communicates with the pump inlet. Further, a
regulator valve is interposed between the pump outlet and the
regenerative start stage that selectively regulates associated flow
from the regenerative start stage. The associated method include
directing flow from the centrifugal pump to a regenerative start
stage in order to supply an associated downstream flow circuit.
During low speed starting, a portion of the flow from the
regenerative start stage is provided to an ejector that
recirculates to an inlet of the centrifugal pump. Once the
centrifugal pump provides a predetermined level of at least one of
the flow and pressure requirements of the associated flow circuit,
the method includes terminating flow from the regenerative start
stage.
Inventors: |
Clements; Martin A.; (West
Chester, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EATON INTELLIGENT POWER LIMITED |
DUBLIN |
|
IE |
|
|
Family ID: |
67843759 |
Appl. No.: |
16/295418 |
Filed: |
March 7, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62639745 |
Mar 7, 2018 |
|
|
|
62666905 |
May 4, 2018 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 9/044 20130101;
F04D 13/12 20130101; B64D 37/14 20130101; F04D 5/007 20130101; F04D
7/02 20130101; B64D 37/005 20130101; F02M 59/447 20130101; F04D
15/0209 20130101; F02M 37/048 20130101; F04D 5/002 20130101; F02C
7/236 20130101 |
International
Class: |
F02M 59/44 20060101
F02M059/44; B64D 37/00 20060101 B64D037/00; F02M 37/04 20060101
F02M037/04; F04D 5/00 20060101 F04D005/00; F04D 7/02 20060101
F04D007/02; F04D 15/02 20060101 F04D015/02 |
Claims
1. A pump system comprising: a pump including an inlet and outlet
that communicate with a rotary kinetic pumping element for
imparting energy to an associated pump fluid directed toward an
associated downstream flow circuit; a regenerative start stage in
selective fluid communication with the pump; a valve that precludes
fluid communication between the pump outlet and the associated
downstream flow circuit until the pump reaches one of a
predetermined pressure or flow threshold; an ejector having an
inlet that communicates with the pump outlet and an outlet that
communicates with the pump inlet; and a regulator valve that
selectively regulates associated fluid to the regenerative start
stage, wherein the valve is responsive to a signal taken from
between the pump outlet and the valve.
2. The pump system of claim 1 wherein the regulator valve is also
responsive to a second pressure signal from upstream of the pump
inlet.
3. The pump system of claim 1 wherein the regulator valve is
configured to supply inlet flow to the regenerative start stage
until the pump provides at least one of predetermined flow and
pressure requirements of the associated downstream flow
circuit.
4. The pump system of claim 1 wherein the regulator valve receives
flow directly from a system fluid source.
5. The pump system of claim 1 wherein the ejector receives flow
from the regenerative start stage during start-up.
6. The pump system of claim 1 wherein the ejector recirculates flow
from the pump outlet to the pump inlet.
7. The pump system of claim 1 wherein the regenerative start stage
contributes flow to both the ejector and the associated downstream
flow circuit during start-up.
8. The pump system of claim 7 wherein the ejector receives flow
from the regenerative start stage during start-up and is configured
to recirculate the flow to the pump inlet.
9. The pump system of claim 8 wherein the ejector receives flow
from the regenerative start stage until the pump provides at least
one of predetermined flow and pressure requirements of the
associated downstream flow circuit, and thereafter the ejector
evacuates fluid from the regenerative start stage and thereby
decouples the regenerative start stage from the pump system.
10. The pump system of claim 1 wherein the regenerative start stage
receives system fluid through the regulator valve in a valve open
position.
11. A method of providing flow to a flow circuit during start-up
and transitioning to flow from a centrifugal pump, the method
comprising: providing fuel from a fuel source to the centrifugal
pump; during low speed starting of approximately less than 10% of
engine shaft speed, directing flow from the fuel source to a
regenerative start stage in order to supply an associated
downstream flow circuit; during the low speed starting, a portion
of the flow from the regenerative start stage is provided to an
ejector that recirculates to an inlet of the centrifugal pump; and
once the centrifugal pump provides a predetermined level of at
least one of the flow and pressure requirements of the associated
flow circuit, terminating flow from the regenerative start stage to
the associated main flow circuit.
12. The method of claim 11 wherein once the centrifugal pump
provides the predetermined level of at least one of the flow and
pressure requirements of the associated downstream flow circuit,
the ejector removes fluid from the regenerative start stage in
order to isolate the regenerative start stage from the system.
13. The method of claim 12 wherein a transition from flow
requirements for the flow circuit includes initially supplying
pressurized flow from the regenerative start stage and subsequently
supplying pressurized flow from the centrifugal pump, and
transitioning occurs when an outlet pressure of the centrifugal
pump exceeds a pressure output of the regenerative start stage.
14. The method of claim 13 wherein once the centrifugal pump
provides the predetermined level of at least one of the flow and
pressure requirements of the associated downstream flow circuit,
the ejector empties fluid from the regenerative start stage in
order to isolate the regenerative start stage from the associated
flow circuit.
15. The method of claim 11 further comprising regulating flow from
the fuel source through the regenerative start stage based on
monitoring a pressure differential between an inlet and outlet
pressure of the centrifugal pump.
16. The method of claim 11 further comprising driving the
centrifugal pump and the regenerative start stage from a common
shaft, and selectively reducing the power consumed by the
regenerative start stage after start-up.
Description
[0001] This application claims the priority benefit of U.S.
provisional applications, Ser. No. 62/639,745, filed Mar. 7, 2018
and 62/666,905, filed May 4, 2018, the disclosures of which are
expressly incorporated herein by reference.
BACKGROUND
[0002] This invention relates to a fluid pump system, and
particularly a pumping system requiring different demands at
start-up. More particularly, this invention relates to an aircraft
engine fuel system that employs a high-speed centrifugal pump, and
one that addresses the need to perform engine starting, i.e.,
provide adequate flow and pressure at a low drive speed.
[0003] High-speed centrifugal pumps have distinct advantages in
minimizing aircraft engine fuel pump weight and manufacturing cost.
For these reasons, fuel system designers have attempted to
incorporate the high-speed centrifugal pump into aircraft engine
fuel systems. These attempts are most often found inadequate due to
the inability of the high speed centrifugal pump to perform engine
starting. That is, engine starting requires sufficient flow and
sufficient pressure at a low drive speed. Assistance from a second
engine or start pump is generally used to perform the engine start.
In most cases, the second pump increases both system weight and
cost, thereby negating the reasons to use the high-speed
centrifugal pump. Further issues arise from the need to disengage
the start pump so as not to create an excessive amount of pumping
energy that must be absorbed as heat into the fuel system.
[0004] Systems previously proposed have undesirable modes which
allow the regenerative stage to remain engaged in pumping fluid to
the fuel system. Should this occur, the prior systems that
incorporate regenerative stages could undesirably produce system
pressures far in excess of the system needs, and thus it would be
desired to have an arrangement that self-limits pressure production
and thereby protects the fuel system from the potential of
over-pressurization.
[0005] A need exists for an improved arrangement that addresses at
least one or more of the above-described problems. That is, it
would be desirable to provide secondary pumping function for
start-up purposes that would not negate the weight and cost
advantages of the high speed centrifugal pump, while advantageously
retaining the advantages and benefits of using the high-speed
centrifugal pump in an engine fuel system, and that protects a fuel
system from the potential of over-pressurization.
SUMMARY
[0006] An engine fuel system is provided that addresses the need
for a secondary pumping function for start-up purposes, and that
does not negate the weight and cost advantages of a high speed
centrifugal pump.
[0007] The engine fuel system uses a regenerative type pump
element, an ejector pump, and a series of valves to control the
start process in conjunction with the high-speed centrifugal
pump.
[0008] The engine fuel or pump system includes a pump having an
inlet and outlet that communicate with a rotary kinetic pumping
element for imparting energy to an associated fluid for an
associated downstream flow circuit. A regenerative start stage is
in selective fluid communication with the pump. An ejector includes
an inlet that communicates with the pump outlet and an outlet that
communicates with the pump inlet. Further, a regulator valve is
interposed between the pump outlet and the regenerative start stage
that selectively controls associated flow from the regenerative
start stage.
[0009] The regulator valve communicates with the pump outlet and
selectively directs fluid therefrom to an inlet of the regenerative
start stage.
[0010] The regulator valve is responsive to pressure signals from
the pump outlet and from upstream of the pump inlet.
[0011] The regulator valve is configured to monitor flow from the
pump outlet and supply inlet flow to the regenerative start stage
until the pump provides predetermined flow and/or pressure
requirements of the associated flow circuit.
[0012] The pump and regenerative start stage may be commonly driven
by a first shaft.
[0013] The ejector receives flow from the pump outlet.
[0014] The ejector communicates with the regenerative start stage
in order to scavenge fluid therefrom once the pump provides the
predetermined flow and/or pressure requirements for the associated
flow circuit.
[0015] The ejector recirculates flow from the pump outlet to the
pump inlet.
[0016] The regenerative start stage is in fluid communication with
both the ejector and the associated downstream flow circuit so that
during start-up, the regenerative start stage contributes flow to
both the ejector and the associated downstream engine fuel
system.
[0017] The ejector receives flow from the regenerative start stage
during start-up and is configured to recirculate flow from the
regenerative start stage to the pump inlet.
[0018] The system provides flow from the regenerative start stage
until the pump provides at least one of predetermined flow and
pressure requirements of the associated downstream flow circuit,
and thereafter the ejector evacuates fluid from the regenerative
start stage and thereby decouples the regenerative start stage from
the pump system.
[0019] The system further includes a first check valve downstream
of the centrifugal pump outlet that is biased toward a closed
position so that when in a closed position, flow from the
centrifugal pump outlet is directed to the regulator valve of the
regenerative start stage.
[0020] The first check valve opens when the pump reaches at least
one of predetermined flow and pressure requirements of the
associated downstream engine fuel system.
[0021] The system further includes a second check valve downstream
of the regenerative start stage that allows flow from the
regenerative start stage during start-up.
[0022] A method of providing flow to an associated downstream flow
circuit during start-up and transitioning to flow from a
centrifugal pump is provided.
[0023] The method includes providing fuel from a fuel source to the
centrifugal pump. During low speed starting of approximately less
than 10% of engine shaft speed, the method includes directing flow
from the centrifugal pump to a regenerative start stage in order to
supply an associated engine fuel system (flow circuit). During the
low speed starting, a portion of the flow from the regenerative
start stage is provided to an ejector that recirculates to an inlet
of the centrifugal pump. Once the centrifugal pump provides a
predetermined level of at least one of the flow and pressure
requirements of the associated flow circuit, the method includes
terminating flow from the regenerative start stage to the
associated flow circuit.
[0024] Once the centrifugal pump provides the predetermined level
of at least one of the flow pressure requirements of the associated
flow circuit/engine fuel system, the ejector empties fluid from the
regenerative start stage in order to isolate the regenerative start
stage from the associated flow circuit/engine fuel system.
[0025] The method further includes transitioning flow requirements
for the associated engine fuel system from initially supplying flow
from the regenerative start stage to subsequently supplying the
associated flow circuit/engine fuel system from the centrifugal
pump, wherein the transitioning occurs when an outlet pressure of
the centrifugal pump exceeds a pressure output of the regenerative
start stage.
[0026] Once the centrifugal pump provides the predetermined level
of at least one of the flow pressure requirements of the associated
flow circuit/engine fuel system, the ejector empties fluid from the
regenerative start stage in order to isolate the regenerative start
stage from the associated flow circuit/engine fuel system.
[0027] The method further includes regulating flow from the
centrifugal pump through the regenerative start stage based on
monitoring outlet pressure of the pump and inlet pressure to the
centrifugal pump.
[0028] The method further includes driving the centrifugal pump and
the regenerative start stage from a common shaft, and selectively
reducing the power consumed by the regenerative start stage after
start-up.
[0029] A primary advantage relates to minimizing both aircraft
engine fuel pump weight and manufacturing cost by using a
high-speed centrifugal pump with assistance from a second, start-up
pump arrangement that does not negate the advantages of the
centrifugal pump.
[0030] Another benefit resides in the ability to unload the
start-up pump stage from the system once at least one of sufficient
flow and pressure is provided by the--speed centrifugal pump.
[0031] Still another advantage is associated with the ability to
scavenge or evacuate the start-up pump stage cavity in order to
effectively decouple the start-up pump stage from the system.
[0032] Yet another advantage is the ability to protect the system
by limiting/self-limiting the potential for
over-pressurization.
[0033] Still other benefits and advantages of the present
disclosure will become more apparent from reading and understanding
the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a schematic representation of the present
invention.
[0035] FIG. 2 is a modified, self-limiting regenerative pumping
element start stage for a high speed centrifugal engine fuel
pump.
DETAILED DESCRIPTION
[0036] The following description with reference to the accompanying
drawing is provided to assist in a comprehensive understanding of
one or more embodiments of the present disclosure as defined by the
claims and their equivalents. It includes various specific details
to assist in that understanding but these are to be regarded as
merely exemplary. Accordingly, those of ordinary skill in the art
will recognize that various changes and modifications of the
various embodiments described herein can be made without departing
from the scope and spirit of the present disclosure. Various
exemplary embodiments of the present disclosure are not limited to
the specific details of different embodiments and should be
construed as including all changes and/or equivalents or
substitutes included in the ideas and technological scope of the
appended claims. In describing the drawings, where possible,
similar reference numerals are used for similar elements.
[0037] The terms "include" or "may include" used in the present
disclosure indicate the presence of disclosed corresponding
functions, operations, elements, and the like, and do not limit
additional one or more functions, operations, elements, and the
like. In addition, it should be understood that the terms
"include", "including", "have" or "having" used in the present
disclosure are to indicate the presence of components, features,
numbers, steps, operations, elements, parts, or a combination
thereof described in the specification, and do not preclude the
presence or addition of one or more other features, numbers, steps,
operations, elements, parts, or a combination thereof.
[0038] The terms "or" or "at least one of A and/or B" used in the
present disclosure include any and all combinations of words
enumerated with them. For example, "A or B" or "at least one of A
and/or B" means including A only, including B only, or including
both A and B.
[0039] Although the terms such as "first" and "second" used in the
present disclosure may modify various elements of the different
exemplary embodiments, these terms do not limit the corresponding
elements. For example, these terms do not limit an order and/or
importance of the corresponding elements, nor do these terms
preclude additional elements (e.g., second, third, fourth, etc.).
The terms may be used to distinguish one element from another
element. For example, a first mechanical device and a second
mechanical device all indicate mechanical devices and may indicate
different types of mechanical devices or the same type of
mechanical device. For example, a first element may be named a
second element without departing from the scope of the various
exemplary embodiments of the present disclosure, and similarly, a
second element may be named a first element.
[0040] It will be understood that, when an element is mentioned as
being operatively "connected" to or "coupled" to or "in
communication" with another element, the element may be directly
connected to, coupled to, or in communication with another element,
and there may be an intervening element between the element and
another element. To the contrary, it will be understood that, when
an element is mentioned as being "directly connected", "directly
coupled", or "directly communicating" with another element, there
is no intervening element between the element and another
element.
[0041] The terms used in the various exemplary embodiments of the
present disclosure are for the purpose of describing specific
exemplary embodiments only and are not intended to limit different
or various exemplary embodiments of the present disclosure. As used
herein, the singular forms are intended to include the plural forms
as well, unless the context clearly indicates otherwise.
[0042] All of the terms used herein (including technical or
scientific terms) have the same meanings as those generally
understood by an ordinary skilled person in the related art unless
they are defined otherwise. The terms defined in a generally used
dictionary should be interpreted as having the same meanings as the
contextual meanings of the relevant technology and should not be
interpreted as having inconsistent or exaggerated meanings unless
they are clearly defined in the various exemplary embodiments.
[0043] Turning initially to FIG. 1, there is shown a fluid system
100, particularly a pumping system 110 requiring different demands
at start-up. More specifically, a preferred embodiment of this
system 100 is a flow circuit or an aircraft engine fuel system that
includes the pump system 110. The pump system 110 preferably
employs a high-speed pump 112, for example a centrifugal pump,
having a pump inlet 114 and a pump outlet 116. A rotary kinetic
pumping element such as an impeller 118 is schematically
represented in FIG. 1. Those skilled in the art will appreciate
that the impeller 118 is received for rotational movement relative
to the centrifugal pump housing (not shown), and that the inlet 114
and outlet 116 are provided at desired locations in the housing and
communicate with a pump cavity that receives the impeller. The
centrifugal impeller is driven by a shaft 130 supported by suitable
bearings 132 in a manner well-known in the art. Fluid, such as
engine fuel, is provided from a suitable fluid source 134. Rotation
of the impeller 118 by the shaft 130 imparts energy to the fluid
where the pressurized fluid is provided for an associated main flow
circuit or engine fuel system 136 via fluid passage 138. Details of
the associated main flow circuit/engine fuel system 136 are
conventional and form no part of the present invention so that
further description herein is unnecessary to a full and complete
understanding of the present disclosure. The impeller 118 is driven
by drive shaft 130 at high speed and may range, for example, from 0
rpm to approximately 35,000 rpm, although the rotational speed of
the impeller should not be deemed to limit the present
invention.
[0044] As noted in the Background, fuel from source 134 is provided
to a centrifugal pump to supply the downstream main flow
circuit/engine fuel system 136. A need exists, however, to address
engine starting or engine start-up issues, i.e., provide adequate
flow and pressure at a low drive speed, particularly when a light
weight, high speed rotary pump such as centrifugal pump 112 is used
in the pumping system 100 and is unable on its own to provide
sufficient flow and/or sufficient pressure at start-up speeds. The
system 100 is modified as shown in FIG. 1 so that the centrifugal
pump 112 supplies pressurized flow through a first check valve 140
(where the check valve includes a conventional biasing member or
biasing spring 142 that imposes a predetermined closing force on
conventional ball member 144) to the main flow circuit 136 via
fluid passage 138 and also supplies a regenerative start stage or
regenerative pump 150 via fluid passage 152 which receives flow
from the centrifugal pump upstream of the first check valve.
[0045] The regenerative pump 150 (sometimes referred to as a
regenerative turbine pump or peripheral pump) preferably has a
rotating impeller 154 with vanes 156 on both sides of a peripheral
portion thereof to generate high head or pressure between an
inlet/suction 158 and outlet/discharge 160. The regenerative start
stage 150 is driven by shaft 130 in the preferred embodiment,
although it will be understood that a separate drive shaft could
also be used. More particularly, pressurized fluid from the
centrifugal pump outlet 116 flows through passage 152 to regulator
valve 170 that is interposed between the centrifugal supply passage
pump outlet 116 and the inlet 158 of the regenerative start stage.
The regulator valve 170 controls, regulates, or limits the pressure
output from the regenerative start stage 150 until the centrifugal
pump 112 catches up i.e., until the centrifugal pump provides at
least one of sufficient flow and/or sufficient pressure required
for the associated downstream flow circuit or downstream engine
fuel system 136. The regulator valve 170 receives pressure signals
from upstream of the centrifugal pump 112 via fluid passage 172 and
also from the pump outlet 138 via fluid passage 174. Until such
time as the regulator valve 170 closes, the regenerative start
stage 150 supplies pressurized flow during start-up to passage 138
through second check valve 180 via fluid passage 162. The second
check valve 180 includes a biasing member or biasing spring 182
that imposes a preselected closing force on ball member 184. In
this manner, startup flow from the regenerative start stage 150
supplies the associated downstream main flow circuit 136, until
such time as the centrifugal pump 112 has developed sufficient flow
and/or pressure to overcome the biasing force of the first check
valve 140 and thereby supply the main flow circuit. At that time,
the second check valve 180 closes to halt the flow of fluid from
the regenerative start stage 150 from supplying pressurized fluid
to the associated downstream system 136.
[0046] Further, once the centrifugal pump 112 supplies the main
flow circuit, it is desirable to unload the regenerative start
stage since the fluid passing therethrough would otherwise add
undesirable heat to the system. At the transition point where the
centrifugal stage output pressure is begins to provide to the main
flow circuit, in addition to the first check valve opening, flow
from the regenerative start stage is reduced to zero by closure of
the regulator valve 170. Thus, further flow from the centrifugal
stage 112 does not reach the inlet 158 of the regenerative start
stage 150. As is also illustrated in FIG. 1, during start-up a
portion of the flow from the pump discharge 138 is directed as a
motive flow source to an ejector pump 200, namely a first or inlet
port 202 thereof. A second or outlet/discharge port 204
recirculates flow from the ejector 200 via fluid passage 206 to
supply passage 208 that communicates with the inlet 114 of the
centrifugal pump 112. As noted above, fluid passage 172
communicates with the supply passage 208 to the regulator valve 170
so that once the regulator valve closes, all flow from the ejector
200 recirculates to the inlet 114 of the centrifugal pump 112.
Since flow to the inlet port 202 of the ejector 200 is now provided
by the centrifugal pump 112 after check valve 140 opens, the
scavenge port 210 of the ejector 200 now has the capacity to
evacuate the regenerative stage pumping cavity. Removal of the
fluid from the regenerative stage pumping cavity results in any of
the pumping power consumed by the regenerative start stage to be
brought near zero thus effectively decoupling the regenerative
start stage 150 from the system 100. In this manner, pumping
capacity for the flow circuit 136 effectively transitions from the
regenerative start stage 150 to the centrifugal pump 112.
[0047] The system schematically illustrated in FIG. 1 provides the
secondary or start up pumping function via the regenerative start
stage 150 in a manner that does not negate the weight and cost
advantages of the high-speed centrifugal pump 112. The combination
of the regenerative start stage 150, ejector pump 200, regulator
valve 170, and check valves 140, 180 effectively and efficiently
control the start process.
[0048] The associated method of providing flow to the main flow
circuit during start-up and transitioning to the centrifugal pump
is as follows. Fuel enters the high-speed centrifugal pumping stage
112 at pressure levels created by the supply, i.e., the airframe
fuel system. The fuel is pressurized by the centrifugal pump
action. In the case of low speed starting, typically less than 10%
of shaft speed, the centrifugal stage 112 provides very little in
the way of fuel pressurization. Fuel exiting the centrifugal stage
112 feeds both the regenerative start stage 150 through the start
stage regulator valve 170, and the main flow circuit 136 via the
first check valve 140.
[0049] Flow entering the regenerative start stage 150 is
pressurized significantly by the regenerative pump element 154.
This flow exits the regenerative start stage through a second check
valve 180 and enters the main flow circuit 136. The regulator valve
170 at the inlet to the regenerative stage 150 acts to throttle the
flow supplied to the regenerative stage and thereby regulates the
total pressurized pumping system 100 during the start phase. As
drive speed increases, the pressure output of the centrifugal stage
approaches and finally overtakes the regulated output of the
regenerative start stage 150. At the point where the centrifugal
stage output pressure overtakes the main circuit pressure level
(sustained by the regulated regenerative stage 150), the first
check valve 140 opens and flow is provided by the centrifugal pump
stage 112 to the main circuit 136. Flow from the regenerative start
stage is reduced to zero by the full closure of the regenerative
stage inlet pressure regulator 170.
[0050] As regenerative start-up stage flow stops, the regenerative
discharge check valve 180 closes and isolates the regenerative
start stage 150 from the system 100. At that point, the ejector
pump 200 which has always been scavenging fluid from the
regenerative start stage discharge, now has the capacity to
completely evacuate the regenerative stage pumping cavity. Upon
evacuation of the regenerative stage pumping cavity, the pumping
power consumed by the regenerative start stage 150 is brought near
zero, thus effectively decoupling the start stage element.
[0051] The regenerative start stage 150 successfully produces
pressure at low speed where the centrifugal stage 112 does not. The
output pressure of the regenerative start stage 150 is regulated
during the ramp up in drive speed. The centrifugal stage 112 then
comes online smoothly without any disturbance in system output
pressure and flow. Moreover, the regenerative start stage
disengages from the remainder of the system by evacuation of the
pump cavity and thereby does not subsequently add excessive pump
energy and heat to the system.
[0052] Turning to FIG. 2, a second embodiment is shown and
described. Like reference numerals with a primed suffix (') will
refer to like components, and new elements will be referenced by
new reference numerals. There is shown a fluid system 100',
particularly a pumping system 110' requiring different demands at
start-up. More specifically, a preferred embodiment of this system
100' is a flow circuit or an aircraft engine fuel system that
includes the pump system 110'. The pump system 110' preferably
employs a high-speed pump 112', for example a centrifugal pump,
having a pump inlet 114' and a pump outlet 116'. A rotary kinetic
pumping element such as an impeller 118' is schematically
represented in FIG. 2. Those skilled in the art will appreciate
that the impeller 118' is received for rotational movement relative
to the centrifugal pump housing (not shown), and that the inlet
114' and outlet 116' are provided at desired locations in the
housing and communicate with a pump cavity that receives the
impeller. The centrifugal impeller 118' is driven by a shaft 130'
supported by suitable bearings 132' in a manner well-known in the
art. Fluid, such as engine fuel, is provided from a suitable fluid
source 134'. Rotation of the impeller 118' by the shaft 130'
imparts energy to the fluid where the pressurized fluid is provided
for an associated main flow circuit or engine fuel system 136' via
fluid passage 138'. Details of the associated main flow
circuit/engine fuel system 136' are conventional and form no part
of the present invention so that further description herein is
unnecessary to a full and complete understanding of the present
disclosure. The impeller 118' is driven by drive shaft 130' at high
speed and may range, for example, from 0 rpm to approximately
35,000 rpm, although the rotational speed of the impeller should
not be deemed to limit the present invention.
[0053] As noted in the Background, fuel from source 134' is
provided to a centrifugal pump to supply the downstream main flow
circuit/engine fuel system 136'. A need exists, however, to address
engine starting or engine start-up issues, i.e., provide adequate
flow and pressure at a low drive speed, particularly when a light
weight, high speed rotary pump such as centrifugal pump 112' is
used in the pumping system 100' and is unable on its own to provide
sufficient flow and/or sufficient pressure at start-up speeds. The
system 100' is modified as shown in FIG. 2 so that the centrifugal
pump 112' supplies pressurized flow through a first check valve
140' (where the check valve includes a conventional biasing member
or biasing spring 142' that imposes a predetermined closing force
on conventional valve or ball member 144') to the main flow circuit
136' via fluid passage 138'. Upstream of the first check valve 140'
is a pressure signal line 152' that branches to a regulator valve
170' in a manner to be described in greater detail below.
[0054] A regenerative start stage or regenerative pump 150'
(sometimes referred to as a regenerative turbine pump or peripheral
pump) is provided. The regenerative pump 150' preferably has a
rotating impeller 154' with vanes 156' on both sides of a
peripheral portion thereof to generate high head or pressure
between an inlet/suction 158' and outlet/discharge 160'. The
regenerative start stage 150' is driven by shaft 130' in the
preferred embodiment, although it will be understood that a
separate drive shaft could also be used. More particularly, fluid
from the source 134' flows through passage 174' to regulator valve
170' that communicates with the inlet 158' of the regenerative
start stage. The regulator valve 170' controls, regulates, or
limits the pressure output from the regenerative start stage 150'
until the centrifugal pump 112' catches up i.e., until the
centrifugal pump provides at least one of sufficient flow and/or
sufficient pressure required for the associated downstream flow
circuit or downstream engine fuel system 136'. Specifically, the
regulator valve 170' receives pressure signals from upstream of the
centrifugal pump 112' via fluid passage 172' and also from the pump
outlet 116' via fluid passage 152'. Until such time as the
regulator valve 170' closes (when sufficient pressure is provided
through signal passage 152' to urge valve member or valve spool
176' to a closed position that overcomes the biasing force of the
spring 178' in the regulator valve), the regenerative start stage
150' supplies pressurized flow during start-up to passage 138'
through second check valve 180' via fluid passage 162'. The second
check valve 180' includes a biasing member or biasing spring 182'
that imposes a preselected closing force on ball member 184'. In
this manner, startup flow from the regenerative start stage 150'
supplies the associated downstream main flow circuit 136' until
such time as the centrifugal pump 112' has developed sufficient
flow and/or pressure to overcome the biasing force of the first
check valve 140' and thereby supply the main flow circuit. At that
time, the second check valve 180' closes to halt the flow of fluid
from the regenerative start stage 150' from supplying pressurized
fluid to the associated downstream system 136'.
[0055] Further, once the centrifugal pump 112' supplies the main
flow circuit, it is desirable to unload the regenerative start
stage 150' since the fluid passing therethrough would otherwise add
undesirable heat to the system. At the transition point where the
centrifugal stage output pressure begins to provide flow to the
main flow circuit, in addition to the first check valve 140'
opening, flow from the regenerative start stage is reduced to zero
by closure of the regulator valve 170'. Thus, further flow from the
fluid source 134' does not reach the inlet 158' of the regenerative
start stage 150'. As is also illustrated in FIG. 2, during start-up
a portion of the flow in fluid line 138' is directed as a motive
flow source to an ejector pump 200', namely a first or inlet port
202' thereof. A second or outlet/discharge port 204' recirculates
flow from the ejector 200' via fluid passage 206' to supply passage
208' that communicates with the inlet 114' of the centrifugal pump
112'. As noted above, once the regulator valve 170' closes, all
flow from the ejector 200' recirculates to the inlet 114' of the
centrifugal pump 112'. Since flow to the inlet port 202' of the
ejector 200' is now provided by the centrifugal pump 112' after
check valve 140' opens, the scavenge port 210' of the ejector 200'
now has the capacity to evacuate the regenerative stage pumping
cavity. Removal of the fluid from the pumping cavity of the
regenerative stage pump 150' results in any of the pumping power
consumed by the regenerative start stage to be brought near zero
thus effectively decoupling the regenerative start stage 150' from
the system 100'. In this manner, pumping capacity for the flow
circuit 136' effectively transitions from the regenerative start
stage 150' to the centrifugal pump 112'.
[0056] Thus, in this second embodiment of FIG. 2, fluid is supplied
to the inlet of the regenerative stage from pump inlet pressure
instead of from the centrifugal stage discharge (FIG. 1). In doing
so, complete filling of the regenerative stage 150' only occurs up
to a certain shaft speed based mainly upon, for example, the
regenerative wheel diameter and pump inlet pressure-which is not
changing with pump speed. Therefore, a wheel diameter can be
matched or paired with the desired cut off speed of the starting
regenerative stage, thereby self-limiting the pressure producing
process and protecting the fuel system from over
pressurization.
[0057] The system schematically illustrated in FIG. 2 provides the
secondary or start-up pumping function via the regenerative start
stage 150' in a manner that does not negate the weight and cost
advantages of the high-speed centrifugal pump 112'. The combination
of the regenerative start stage 150', ejector pump 200', regulator
valve 170', and check valves 140', 180' effectively and efficiently
control the start process, and advantageously does so in a manner
that limits the process of producing pressure and thereby protects
the fuel system from over-pressurization.
[0058] The associated method of providing flow to the main flow
circuit during start-up and transitioning to the centrifugal pump
in connection with the FIG. 2 embodiment is as follows. Fuel enters
the high-speed centrifugal pumping stage 112' at pressure levels
created by the supply, i.e., the airframe fuel system. The fuel is
pressurized by the centrifugal pump action. In the case of low
speed starting, typically less than 10% of shaft speed, the
centrifugal stage 112' provides very little in the way of fuel
pressurization. Fuel exiting the centrifugal stage 112' feeds the
main flow circuit 136' via the first check valve 140', and also
provides a pressure signal to the regulator valve 170'.
[0059] Flow entering the regenerative start stage 150' via passage
174' from the airframe fuel system supply 134' is pressurized
significantly by the regenerative pump element 154'. This flow
exits the regenerative start stage through a second check valve
180' and enters the main flow circuit 136'. The regulator valve
170' at the inlet to the regenerative stage 15'0 acts to throttle
the flow supplied to the regenerative stage and thereby regulates
the total pressurized pumping system 100' during the start phase.
As drive speed increases, the pressure output of the centrifugal
stage 112' approaches and finally overtakes the regulated output of
the regenerative start stage 150'. At the point where the
centrifugal stage output pressure overtakes the main circuit
pressure level (sustained by the regulated regenerative stage
150'), the first check valve 140' opens and flow is provided by the
centrifugal pump stage 112' to the main circuit 136'. Flow from the
regenerative start stage 150' is reduced to zero by the full
closure of the regenerative stage inlet pressure regulator 170' as
a result of the increased pressure from the outlet 116' of the
centrifugal stage 112' via signal line 152' acting on the valve
spool 176' to overcome the force of spring 178'.
[0060] As flow from the regenerative start-up stage 150' stops, the
regenerative discharge check valve 180' closes and isolates the
regenerative start stage 150' from the system 100'. At that point,
the ejector pump 200' which has always been scavenging fluid from
the regenerative start stage discharge, now has the capacity to
completely evacuate the regenerative stage pumping cavity. Upon
evacuation of the regenerative stage pumping cavity, the pumping
power consumed by the regenerative start stage 150' is brought near
zero, thus effectively decoupling the start stage element.
[0061] The regenerative start stage 150' successfully produces
pressure at low speed where the centrifugal stage 112' does not.
The output pressure of the regenerative start stage 150' is
regulated during the ramp up in drive speed. The centrifugal stage
112' then comes online smoothly without any disturbance in system
output pressure and flow. Moreover, the regenerative start stage
150' disengages from the remainder of the system by evacuation of
the pump cavity and thereby does not subsequently add excessive
pump energy and heat to the system.
[0062] This written description uses examples to describe the
disclosure, including the best mode, and also to enable a person
skilled in the art to make and use the disclosure. Other examples
that occur to those skilled in the art are intended to be within
the scope of the invention if they have structural elements that do
not differ from the same concept, or if they include equivalent
structural elements with insubstantial differences.
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